Typically, add-ins and app packages must be digitally signed before they can be deployed. Instructions provided describe the steps to sign an ArcMap add-in.
In Windows File Explorer, go to C:\Program Files (x86)\Common Files\ArcGIS\bin\ and click EsriSignAddIn.exe.
If ArcObjects has not been installed on the local machine, the EsriSignAddIn executable file may not be present in the indicted path. In that case, the EsriSignAddIn.exe is available by downloading it from the Python Add-In Wizard. Once the EsriSignAddIn.exe has been downloaded, it must be moved to the location indicated above.
In the Welcome screen of the Esri Digital Signature Wizard, click Next and click the Browse button to go to where the Esri add-In file is located.
Click Next, select a certificate from the store (this certificate must be installed) and click Finish. The add-in should now be signed.
Install the add-in. Locate the path of the add-in file (the same path as step 2).
Double-click the file and the installation utility starts. The digital signature area should be populated with the signature the add-in was just signed with.
Click Install and the add-in is now authenticated.
Go to the Add-In Manager located in ArcMap's Customize menu and the installed add-in should have an authenticated digital signature.